Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

There are no annotations provided, so the description carries the full burden of behavioral disclosure. The description indicates this is a creation operation (shortening a URL) and mentions the return of a short link, but it does not disclose potential side effects (e.g., the link is stored), any rate limits, or whether the label is required for tracking. This is a significant gap for a tool that creates a resource.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise: one sentence for the function and one for usage guidance. It front-loads the core action ('Shorten a long URL using KooLink') and then explains when to use it. There is no unnecessary filler, but it could be slightly more structured by separating the usage guidance clearly. Overall, it is efficient and informative.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given that there is no output schema, the description should clarify what the tool returns beyond just 'a compact kool.ink short link.' It does not mention whether the response includes additional data (e.g., the original URL, expiry, or labels). Since this is a creation tool (non-read-only) with no annotations, more detail on side effects, persistence, and the exact return format would be helpful. The description is adequate but not complete for an agent to anticipate the tool's full behavior.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, meaning both parameters (url and label) are described in the schema. The description does not add much beyond what the schema already provides; it confirms that the 'url' is the destination to shorten, but the schema already states that. The label's purpose is adequately explained in the schema as 'Optional label for the API key owner's records.' Thus, the description adds minimal value, but the schema covers the semantics, so a baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function: it shortens a URL using KooLink and returns a kool.ink short link. It distinguishes itself from siblings by focusing on the creation of a short link, whereas siblings likely handle statistics and listing. However, it does not explicitly mention the sibling tool names, so some distinction is implicit rather than explicit.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit usage context: 'Use this whenever the user wants a shortened URL, a tidy link to share, or a redirect for a long destination.' This gives clear guidance on when to invoke the toolcheduling, though it does not discuss situations when NOT to use it (e.g., when only stats are needed). The mention of alternatives is absent, but the context signals list sibling tools, so an agent can infer the distinction.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.